Morpho-histological and ultra architectural changes during early development of endangered golden mahseer Tor putitora

Ambient ultraviolet-B exposure brings quantum changes in phenotypic and molecular signatures of the embryo of a high-altitude fish, Tor putitora

Effects of environmentally relevant ultraviolet B (UVB) light on the embryonic development of a high-altitude dwelling endangered fish, Tor putitora (golden mahseer), were investigated for the first time. For that, three sets of embryos (in triplicates) were exposed to various ambient UVB light doses (1, 2 and 3 W/m2, corresponding to 3.6, 7.2 and 10.8 kJ/m2/day) for 1 h at two different embryonic stages (1 hpf-hours post fertilization and 32 hpf). Another set of embryos was exposed to visible light for the same duration and served as the light control (LC), and the last set was kept under ideal dark conditions for incubation (the dark control, DC). The results showed that the higher levels of UVB light (> 2 W/m2) decreased the hatching rate and survival of embryos and hatchlings, extended the hatching window or hatching time and caused embryonic and hatching deformities. The qPCR analysis revealed upregulation of genes such as nf-kb2, il-1β, tnfα, tlr5, nrf2, bcl2, caspase9, p53, ddb2, mmp13a, mc1r and hsp70 in a dose-dependent manner upon UVB exposure. Overall, the high ambient level of UVB exposure (3 W/m2, equivalent to 10.8 kJ/m2/day) in golden mahseer embryos proved to be lethal or sub-lethal, which were mediated by (or related to) immunological changes, oxidative stress, apoptosis, DNA damage and aberrant development. Further, harmful effects of UVB were found to be stage-dependent and were more significant at 32 hpf. The study is the first preliminary report, at the molecular level, on the impact of environmentally occurring UVB on the embryonic development of an endangered fish species, the golden mahseer.

Molecular characterization of non-specific immune genes of endangered golden mahseer (Tor putitora) and their expression during embryonic and larval development

The present study was undertaken to characterize and analyze the expression of non-specific immune genes to get an insight into the early immune status of endangered golden mahseer. In this study, the full-length mRNA sequence of IFNγ, TNFα, C3, and IL10 was 927, 1409, 5125 and 1177 bp with an ORF of 558, 765, 4938, and 540 bp, encoding a putative protein of 185, 254, 1645, and 179 amino acid residues, respectively. The deduced amino acid sequences of these genes shared highly conserved structures with those from other cyprinids. Ontogenic real-time qPCR results indicated that expression of IFNγ and TNFα was lower until the morula stage and increased from blastula stage and found maximum at the organogenesis stage. Expression of the C3 gene was lower until the gastrula stage, followed by a linear increase from organogenesis to the pre-metamorphosis stage. The expression of IL10 was significantly lower during early developmental stages (till gastrula stage) and reached maximum at organogenesis. The level of IL1β was found maximum in unfertilized eggs and remained elevated till the morula stage. TLR4 expression remained lower during the initial developmental stages and reached the maximum at the organogenesis stage. The expression level of defensin1 was substantially low until the organogenesis stage. In comparison, hepcidin1 was found considerably high until the blastula stage and remained significantly lower during later stages of development. Overall, the data generated improves knowledge on the immune status of endangered golden mahseer during embryonic and larval development, which may help develop effective immunomodulatory interventions during nursery rearing of golden mahseer to produce fry with better fitness.

Evaluation of the acute toxicity of Thymus linearis ethanol extract and its effect on the hemato-biochemical and behavioural response of the Golden mahseer, Tor putitora (Hamilton, 1923)

The present investigation was conducted to estimate the acute toxicity of Thymus linearis plant extract, its effect on hemato-biochemical parameters and behavioural response in the golden mahseer (Tor putitora). The phytochemical composition present in T. linearis plant extrat were Alkaloids, Flavonoids, Phenols and Tannin. The fishes were subjected to eight different concentrations of T. linearis leaves extract (8.25, 8.50, 8.75, 9.00, 9.25, 9.50 and 9.75 mg/kg) and the control group without plant extract for 96-h LD50 study. The mortality was recorded every 24 h post-treatment. Minimum mortality was recorded in the 8.25 mg/kg, whereas 100% mortality was recorded in the 9.75 mg/kg T. linearis extract after 96-h periods. The LD₅₀ was estimated by probit analysis, and the value of T. linearis at 96 h was found to be 8.71 mg/kg for golden mahseer. A non-lethal dose of 1/10th of 96-h LD50 value (0.87 mg/kg) was taken for the sublethal study. After 96 h, the red blood cell (RBC), white blood cell (WBC), haemoglobin (Hb), packed cell volume (PCV) and blood glucose were measured. RBC (×10⁶/mm³), Hb (%) and PCV (%) significantly decreased at 8.25, 8.50, 8.75, 9.00 mg/kg, but WBC and blood glucose significantly increase at 8.25, 8.50, 8.75, 9.00 mg/kg of T. linearis plant extract. The observations on behaviour response of golden mahseer were also recorded. In the present study, the acute toxicity of wild ajwain was more significant than short-term toxicity. The mortality rate was very high during the study period of T. linearis exposure.